Many people and politicians of different countries of North America and South America had thought of an organization of their countries. These countries have also formed different organizations from time to time. Beginning from 1889-1890, these countries held meetings known as the International Conference of American States. At its first conference, 18 countries formed the International Union of American Republics.

In 1910, these countries held the Fourth International Conference of American States at Buenos Aires. They changed the name of the International Union of American Republics to the Union of American Republics. These countries held the ninth International Conference of American States between March and May 1948 at Bogotá. On 30th April 1948, 21 countries signed an agreement. They called this agreement the Charter of the Organization of American States. This was the beginning of the Organization of American States (OAS). OAS started functioning from December 1951.

The Charter of the OAS states the goals for forming the OAS. There are many goals. Some important goals relate to peace and security for these countries; development of democratic governments; and economic cooperation.

The later expansion of the OAS included the newly independent nations of the Caribbean (most of whom gained independence only after World War II) and Canada. Members with later admission dates (sorted chronologically):